This invention pertains to the art of windows embodying fixed or ventilator sash or fixed glazing in a wall structure, such as may be suitable for residential, apartment, commercial or other types of buildings. More specifically, the invention relates to the formation and application of a muntin bar unitary frame forming a decorative grille or lattice and for positioning in confronting planar relationship to a glass pane to provide a visual appearance for the window of a divided glass assembly, such as in a window of Colonial, Georgian, or other architectural tradition.
Location of a muntin bar unitary frame in confronting and planar relationship to a large glass pane, or inside of a multiple pane insulating glass unit, is common practice. This invention relates specifically to the design and structural formation of such a frame.
Heretofore decorative frames intended to simulate the appearance of muntin bars have been die-moulded in thermoplastic material and have been quite practical in application to window sash. Due to the very wide range of sash shapes and sizes now required, particularly for large glass areas, and, in turn, high tooling costs, one-piece moulded plastic frames are generally uneconomical for residential-type windows.
In residential construction, the use of windows glazed with hermetically sealed double pane insulating glass units is rapidly increasing. By positioning an insert type divider grille or muntin bar unitary frame in the cavity between the glass panes, the visual appearance of the glazed window sash may be that of a multiple pane unit, yet the inside and outside glass surfaces are large, flat and easy to clean. It has been common practice to manufacture insert type divider frames from plastic extrusions of tubular bar formation. Such frames may comprise several overlapping and mortised diagonal bars, or vertical and horizontal crossjointed bars, united at the ends thereof to a perimetrical edge bar structure. Frames of such type may include several bar members and joints which limit rigidity and strength; require precise and painstaking assembly, including difficult bonding procedures; and very careful handling when coordinating same with a process of manufacturing insulating glass units. Accordingly, production costs are excessive for rectangular-shaped units, and uneconomical for frames of diamond configuration.